The present invention is directed to a fluid cylinder flow control for controlling the speed at which a piston moves within the cylinder.
Fluid power cylinders have found widespread usage in many different applications. In most of these applications, the speed at which the cylinder operates, e.g. at which the piston moves relative to the cylinder, is controlled by a device generally referred to as a flow control. These flow controls typically operate to throttle the rate at which the fluid, whether it be gas or liquid, is exhausted from the cylinder when the cylinder and/or piston are moved relative to each other.
Typically, flow controls are provided at both ends of the cylinder to control the piston speed for movement in either direction. These flow controls may be either valve mounted, port mounted or mounted in line. The majority of them are port mounted in which a needle throttle valve or the like is mounted at the cylinder by threading it into a port on each of the cylinder end cap closures, and the needle valve may be adjusted to control the fluid flow rate. In the valve mounted flow controls the flow control is mounted remote from the cylinder at the fluid control valves which are utilized to control the operation of the cylinder, for example at an operator control station. In the in line mounted flow controls the flow controls are positioned in the conduit between the control valves and the cylinder and also relatively remote to the cylinder.
A principal disadvantage of the port mounted needle valve flow controls is their size. In the standard systems these flow controls may protrude from the cylinder end cap closures by as much as 31/2-4 inches. Even where these flow controls are miniaturized, they still protrude from the cylinder by as much as 1-11/4 inches. However, as industry moves toward more and more miniaturization, these considerable protrusions are undesirable and unacceptable, particularly where the flow controls are on the cylinders as they are when they are port mounted.
Another potential disadvantage of the prior needle throttle valve flow controls, whether they be port, valve or in-line mounted, is that their range of adjustment is relatively narrow. For example, adjustment between 0-100 percent flow typically occurs in only 4-8 turns of the needle valve. It would be desirable if the flow controls, particularly where they have been miniaturized as is now possible to some extent, could be more precisely and accurately controlled.
In the present invention the aforementioned disadvantages are obviated. In the present invention, protrusion of the flow controls from the cylinder is eliminated thereby making possible the maximum degree of miniaturization of the cylinder. Moreover, the flow controls incorporating the principles of the present invention are capable of substantially greater and more precise adjustment of as much as 300-400 percent better than the flow controls of the prior art as discussed earlier. Where the flow controls of the prior art typically achieve their complete adjustment over the range of 0-100 percent flow in a mere 4-8 turns, the adjustment of the flow controls over the 0-100 percent range in the present invention may be accomplished in 18-20 turns. Accordingly, fine and accurate fluid control adjustment is substantially improved in the flow controls of the present invention. Finally, both of these important aforementioned advantages are possible at less expense and simpler construction than the prior flow control systems.
In one principal aspect of the present invention, a fluid flow control for the control of the flow of fluid from a fluid cylinder with a fluid operated reciprocating piston therein, includes a rotatable disk positionable in the cylinder. The disk has a thickness and is rotatable within the cylinder about an axis which is substantially parallel to the thickness of the disk. Means is provided for rotating the disk, and at least one arcuate slot which opens through the thickness of the disk communicates fluid through the disk. The slot is substantially concentric to the axis of rotation of the disk and has a width which varies between a maximum width at a first location spaced along the slot, and a minimum width at a second location spaced along the slot from the first location, wherein the flow of fluid can be varied by the rotation of the disk between the first and second locations.
In another principal aspect of the present invention, the means for rotating the disk comprises teeth on the disk and an adjusting element, preferably a screw, which engages the teeth and which rotates the disk upon movement of the adjusting element.
In still another principal aspect of the present invention, an opening is provided through the thickness of the disk at the axis of rotation of the disk for receiving the rod of the piston for reciprocation of the piston rod through the last mentioned opening.
In still another principal aspect of the present invention a pair of the slots are positioned on opposite sides of the axis of rotation of the disk and relative to each other to permit reversal of the direction in which disk faces.
In still another principal aspect of the present invention, the slot is tearshaped so that the aforementioned first and second locations are at opposite ends of the slot.
In still another principal aspect of the present invention, a passage is provided in at least one of the end cap closures of the cylinder and the passage has an opening in the cylinder housing for discharging fluid from the cylinder housing between the piston and one of the end cap closures of the cylinder when the piston moves toward that end cap closure. The slot is arcuate and overlies the opening to the passage whereby the flow of fluid is varied by the rotation of the disk between the first and second locations to control the discharge of fluid to the passage and the speed at which the piston moves toward the end cap closures.
These and other objects, features and advantages of the present invention will be more clearly understood upon consideration of the following detailed description of the preferred embodiment of the invention which will be described to follow.